Ratcheting up the rancour, Hillary Clinton and Bernie Sanders tangled aggressively in a presidential debate Sunday night over trade and Wall Street influence, with Clinton accusing her challenger of turning his back on a rescue of the auto industry and Sanders countering that Clinton's friends on Wall Street had "destroyed this economy."

It was a marked change in tone for the two Democrats, signaling Sanders' increasingly difficult effort to slow the Democratic front-runner. Both candidates frequently interrupted and talked over one another, accusing each other of misrepresenting the other's record.

"Let's have some facts instead of some rhetoric for a change," Clinton snapped at Sanders at one point.

"Let me tell my story, you tell yours," Sanders shot back at another. "Your story is voting for every disastrous trade amendment and voting for corporate America."

Their disagreements were clear, but still the debate's tone was nothing like that of the Republican debate in Detroit just three days earlier, a four-way faceoff that was marked by a steady stream of personal attacks, insults and even sexual innuendo. The Democrats' faceoff, in comparison, was a more civil if heated affair.

Flint's water became tainted with lead when officials switched its supply from Detroit's system to the Flint River in 2014 to save money. (Sarah Rice/Getty Images)

Clinton accused the Vermont senator of voting against a 2009 bailout of the auto industry, saying, "I went with them. You did not. If everybody had voted the way he did, I believe the auto industry would have collapsed, taking 4 million jobs with it."

Sanders countered that the money for the auto industry was part of a larger bailout package for Wall Street, adding, "I will be damned if it was the working people of this country who have to bail out the crooks on Wall Street." He referred to the overall package as "the Wall Street bailout where some of your friends destroyed this economy."

Ultimately, President George W. Bush and Treasury Secretary Hank Paulson agreed to a $23.4 billion US for the auto industry from the federal bailout money for the financial sector.

Sanders also took direct aim at the former secretary of state's paid speeches to Wall Street banks and other financial companies. She promised to release transcripts of her private remarks only if all her opponents — Democratic and Republican — did the same.

Flint's water became tainted when officials switched its supply from Detroit's system to the Flint River in 2014 to save money. The impoverished city's government was under state control at the time.

Bernie Sanders, left, is hoping to score a hit in Michigan with his argument that Hillary Clinton has supported trade deals with 'disastrous' consequences for workers in the state. (Alex Wong, Spencer Platt/Getty Images)

An emotional Sanders said he felt "literally shattered" by the toxic tap water in Flint and renewed his call for Gov. Rick Snyder to resign.

Clinton, who had not previously made that call, added emphatically: "Amen to that," and then said that Snyder should "resign or be recalled."

Clinton had previously made it a point to frame the crisis in the majority-black city in racial terms, saying it never would have taken so long to address the problem in a wealthy, white area.

Both candidates promised tougher federal oversight of water systems if elected. And, asked if anyone should go to jail, both called for holding people accountable at every level of government.

Snyder quickly tweeted that "political candidates" will be leaving Flint and Michigan in a few days after the state's primary but he is "committed to the people of Flint."

In a few days, political candidates will be leaving Flint and Michigan.

Crucial Midwestern primaries coming up

With Clinton continuing to widen her considerable lead in the Democratic delegate count, Sanders sees upcoming Midwestern primaries as a crucial opportunity to slow her momentum by highlighting his trade policies. After Michigan's vote on Tuesday, the March 15 primaries include Ohio, Illinois and Missouri.

Just as the debate got underway, Sanders received the welcome news that he had won the Democratic caucuses in Maine, not far from his home state of Vermont. That gives him victories in eight states to 11 wins for Clinton. But the more lopsided delegate count suggests Clinton is on a steady march toward the nomination. Sanders has struggled to broaden his appeal beyond the liberals and young voters attracted to his campaign.

Clinton has at least 1,130 delegates to Sanders' 499, including superdelegates -- members of Congress, governors and party officials who can support the candidate of their choice. It takes 2,383 delegates to win the nomination.

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